Gas springs are used, inter alia, to dampen the relative movement between two movable parts. One example of such use is found in so-called sun-bed constructions in which the upper part, or canopy, of the bed structure can be moved between a position in which the canopy lies essentially contiguous with the bottom part of said structure, i.e. the bed surface, and an upwardly swung position, in which the canopy is positioned at an angle to the bed surface.